The drinking? It's not a bad thing to have an occasional drink, Mighty. It's just that if it makes things harder or brings up emotions you aren't needing to deal with right now, it might be better to wait and find a different outlet. Sweating is always helpful.
The conversations? Your kids never had a say in the break up of their family. The parent that is stable is about to undergo some surgery, i.e. she isn't superhuman and impermeable.
It may help to let them be part of it. To experience the emotions with somebody they can be safe with and can show them how to deal with the emotions. How to deal with life and all that comes with it.
They are struggling to be adults and as such want more and more say in how things are done concerning their life. Seems natural to me. Also seems natural that you would want to protect them from that. I would (and have).
But somewhere in there is a happy medium. They already know more than you think. More than you do in some aspects. They have feelings. They have less experience with how to deal with those feelings.
The more you can do to include and show, the more they'll learn about life.
They might not like it at first. You might not like it at first. But if you keep at it, it'll get you all where you need to be without the trauma of learning as you go (as much).
That's been my approach. It's paid off with my son. My daughter? Not so much. But I don't doubt that I did what would be most useful to and for both of them. She'll see things differently later when she has her own family I'm sure. And although I didn't do anything to her to make her not want to talk to me, she doesn't want to talk to me - not about anything. It's how she is expressing her anger. For now.
She also knows that I'm a safe place to vent her feelings and thoughts.
Each person is different. Each one takes their own path to get to where they are going. Your kids included. But equipping them to deal with it is helpful for them. Keeping it from them won't work in the long term - they'll just make things up to fill in the gaps Not to say they need to hear opinions. Rather just how you are dealing with things. How you are seeing things. How the adult in their life faces and lives life.
The rest is up to them
AJ
"Our lives begin to end the day we become silent about things that matter" MLK Put the glass down... "Yesterday I was clever so I wanted to change the world Today I am wise, so I am changing myself."
Not to say they need to hear opinions. Rather just how you are dealing with things. How you are seeing things. How the adult in their life faces and lives life. 
